Videoconferencing is defined as a technique for intercommunicating two or more audiovisual end-points interactively, such that video is facilitated between the parties involved. Full two-way audio and video is costly and requires analog video channels or high capacity digital channel. Present day videoconferencing is implemented by using either IP networks or ISDN. A more common configuration is that of Interactive TV, which includes full service out, audio only in. The components of a videoconferencing system end-point is a camera, microphone, video display. Generally, to transmit the required data effectively, a large bandwidth is necessary. It is however possible to use a codec (Compression/Decompression) device, to compress the audio signal and thus get more data for the same available bandwidth. If more then two end-points are involved, a component called MCU (Multipoint Conferencing Unit) must be employed. Such a component is implemented either in software or in hardware, and it allows more than one user to be on the screen at one time. Some such commercial devices can show a multiplicity of users simultaneously, whereas others will switch only to the person who is speaking.
Industry accepted standards for facilitating videoconferencing interconnectivity. The standards are endorsed by the ITU (International Telecommunications Union). The standards are based upon the networking medium that is used to transmit audio, video and data associated with videoconferencing. The H.323 standard is the most common video conferencing standard, implemented in Ethernet and Token-ring LANs, it is used in connection with the IP protocol transport. The H.320 standard relates to multimedia and videoconferencing over ISDN lines.